Chemical Analysis Flashcards
which cations do you test for using the flame method?
Li+, Na+, K+, Ca2+, Cu2+
what cations do you test for using NaOH solution?
NH4+, Cu+, Fe2+, Fe3+, Al3+, Ca2+
Li+ flame colour?
(crimson) red
Na+ flame colour?
orange
K+ flame colour?
lilac
Ca2+ flame colour?
brick red
Cu2+ flame colour?
green
ammonia test?
mix NaOH, heat it up over bunsen burner, and red litmus paper turns blue if positive
Cu2+ and NaOH
creates a blue ppt = Cu(OH)2
Fe2+ and NaOH
creates a green ppt = Fe(OH)2
Fe3+ and NaOH
creates a brown ppt = Fe(OH)3
Al3+ and NaOH
creates a white ppt, but does dissolve excess - so becomes colourless again
Ca2+ and NaOH
creates a white ppt, but doesn’t dissolve excess - stays white
how do you test for sulphates?
adding barium chloride and HCl
why is an acid added for a sulphate test?
gets rid of any unwanted carbonate ions